Question

If two solid-hemisphere s of same base radius r are joined together along their bases , then curved surface area  of this new solid is 

Options

• $$4\pi r^2$$

• $$6\pi r^2$$

• $$3\pi r^2$$

• $$8\pi r^2$$

Answer 1

Base radius of the hemisphere = r
Since the two hemispheres are joined end to end, it becomes a complete sphere. 
Curved surface area of the new solid = total surface area of the sphere.

$$\text{ Curved surface area of the new solid }=4\pi r^2$$